Thin film magnetic head and method of manufacturing the same

ABSTRACT

In order to provide a thin film magnetic head having a high performance as well as a method of manufacturing the same, in which throat height TH of a pole portion and MR height MRH can be formed accurately to have desired design values for improving a surface recording density and reducing a side fringe magnetic flux during a writing, after forming a MR element on a substrate  41, 42,  a first magnetic film  47  is formed on the MR element, a write gap layer  48  is deposited on the first magnetic layer, a thin film coil  50, 52  supported by a coil supporting insulating layer  51, 53  is formed, a second magnetic layer  54  is formed on the insulating layer, non-magnetic side walls  55   a  are selectively formed on side surfaces of a pole portion of the second magnetic layer, a part of the write gap layer in the vicinity of the pole portion and a part of the first magnetic layer are selectively removed by anisotropic etching to form a recess  56  while said pole portion and side walls are used as a mask. The air bearing surface is polished with reference to the inner side wall  56   a  of the recess  56.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin film magnetic head and a methodof manufacturing the same, and more particularly to a combination orcomposite or hybrid type thin film magnetic head constructed by stackingan inductive type thin film writing magnetic head and a magnetoresistivetype reading magnetic head one on the other. The present invention alsorelates to a method of manufacturing such a thin film magnetic head.

2. Description of the Related Art

Recently a surface recording density of a hard disc device has beenimproved, and it has been required to develop a thin film magnetic headhaving an improved performance accordingly. In order to improve aperformance of a reading magnetic head, a reproducing head utilizing amagnetoresistive effect has been widely used. As the reproducingmagnetic head utilizing the magnetoresistive effect, an AMR reproducingelement utilizing a conventional anisotropic magnetoresistive (AMR)effect has been widely used. There has been further developed a GMRreproducing element utilizing a giant magnetoresistive (GMR) effecthaving a resistance change ratio higher than the normal anisotropicmagnetoresistive effect by several times. In the present specification,these AMR and GMR reproducing elements are termed as a magnetoresistivereproducing element or MR reproducing element.

By using the AMR reproducing element, a very high surface recordingdensity of several gigabits per a unit square inch has been realized,and a surface recording density can be further increased by using theGMR element. By increasing a surface recording density in this manner,it is possible to realize a hard disc device which has a very largestorage capacity of more than 10 gigabytes and is still small in size.

A height of a magnetoresistive reproducing element is one of factorswhich determine a performance of a reproducing head including amagnetoresistive reproducing element. This height is generally called MRHeight, here denoted by MRH. The MR height MRH is a distance measuredfrom an air bearing surface on which one edge of the magnetoresistivereproducing element is exposed to the other edge of the element remotefrom the air bearing surface. During a manufacturing process of themagnetic head, a desired MR height MRH can be obtained by controlling anamount of polishing the air bearing surface.

At the same time, a performance of a recording head has been alsorequired to be improved. In order to increase a surface recordingdensity, it is necessary to make a track density on a magnetic recordmedium as high as possible. For this purpose, a width of a pole portionat the air bearing surface has to be reduced to a value within a rangefrom several micron meters to several sub-micron meters. In order tosatisfy such a requirement, the semi-conductor manufacturing process hasbeen adopted for manufacturing the thin film magnetic head. One offactors determining a performance of an inductive type thin film writingmagnetic film is a throat height TH. This throat height TH is a distanceof a pole portion measured from the air bearing surface to an edge of aninsulating layer which serves to separate electrically a thin film coilfrom the air bearing surface. It has been required to shorten thisdistance as small as possible. Also this throat height TH is determinedby an amount of polishing the air bearing surface.

FIGS. 1-13 show successive steps of a known method of manufacturing aconventional typical thin film magnetic head. This magnetic head belongsto a combination type thin film magnetic head which is constructed bystacking an inductive type thin film writing magnetic head and amagnetoresistive type thin film reading magnetic head one on the other.

At first, as illustrated in FIG. 1, on a substrate 11 made of a hardnon-magnetic material such as aluminum-titan-carbon (AlTiC), isdeposited an insulating layer 12 made of alumina (Al₂O₃) and having athickness of about 3-10 μm. Then, as depicted in FIG. 2, a bottom shieldlayer 13 constituting a magnetic shield for protecting the MRreproducing magnetic head from an external magnetic field is formed tohave a thickness of about 2-3 μm on the insulating layer.

Then, after depositing by sputtering a shield gap layer 14 made of analumina with a thickness of 100-150 nm as shown in FIG. 3, amagnetoresistive layer 15 having a thickness of several tens nano metersand being made of a material having the magnetoresistive effect, and themagnetoresistive layer is shaped into a desired pattern by a highlyprecise mask alignment.

Next, as represented in FIG. 4, a shield gap layer 16 having a thicknessof about 100-150 nm is formed such that the electro-magnetic layer 15 isembedded within the shield gap layers 14 and 16.

Then a magnetic layer 17 made of a permalloy and having a thickness of3-4 μm is formed as shown in FIG. 5. This magnetic layer 17 serves notonly as an upper shield layer for magnetically shielding the MRreproducing element together with the above mentioned bottom shieldlayer 13, but also as a bottom magnetic layer of the inductive typewriting thin film magnetic head to be manufactured later. Here, for thesake of explanation, the magnetic layer 17 is called a first magneticlayer, because this magnetic layer constitutes one of magnetic layersforming the thin film writing magnetic head.

Next, as illustrated in FIG. 6, on the first magnetic layer 17, a writegap layer 18 made of a nonmagnetic material such as alumina to have athickness of about 150-300 nm, and then an electrically insulatingphotoresist layer 19 is formed on the write gap layer 18, saidphotoresist layer 19 being shaped into a desired pattern by means of ahighly precise mask alignment.

Next, a first layer thin film coil 20 made of, for instance Cu is formedon the photoresist layer 19.

Next, as depicted in FIG. 7, an electrically insulating photoresistlayer 21 is formed on the thin film coil 20 by a highly precise maskalignment, and then a surface of the photoresist layer 21 is flattenedby baking it at a temperature of, for instance 250° C.

Furthermore, as shown in FIG. 8, on the thus flattened surface of thephotoresist layer 21, a second layer thin film coil 22 is formed. Then,a photoresist layer 23 is formed on the second layer thin film coil 22by a highly precise mask alignment, and a baking process is conductedagain at a temperature of, for instance 250° C.

A reason for forming the photoresist layers 19, 21 and 23 by a highlyprecise mask alignment is that the throat height TH and MR height aredetermined with respect to edges of these photoresist layers on a sideof the pole portion as will be explained later.

Next, as shown in FIG. 9, a second magnetic layer 24 made of, forinstance a permalloy is selectively formed on the write gap layer 18 andphotoresist layers 19, 21 and 23 such that the second magnetic layer hasa thickness of 3-4 μm and is shaped into a desired pattern.

The second magnetic layer 24 is brought into contact with the firstmagnetic layer 17 at a position remote from the pole portion, andtherefore the thin film coil 20, 22 pass through a closed magnetic yokestructure constituted by the first and second magnetic layers. Thesecond magnetic layer 24 includes a pole portion which defines a widthof a track on a magnetic record medium. Furthermore, an overcoat layer25 made of an alumina is deposited on an exposed surface of the secondmagnetic layer 24.

Finally, a side wall 26 of an assembly at which the magneto-resistivelayer 15 and gap layer 8 are formed is polished to form an air bearingsurface (ABS) 27 as shown in FIG. 10. During the formation of the airbearing surface 27, the magnetoresistive layer 15 is also polished toobtain an MR reproducing element 28. In this manner, the above mentionedthroat height TH and MR height MRH are determined by the polishing. Inan actual manufacturing process, contact pads for establishingelectrical connections to the thin film coils 20, 22 and MR reproducingelement 28 are formed, but these contact pads are not shown in thedrawings.

As shown in FIG. 10, an angle θ between a straight line S connectingside edges of the photoresist layers 19, 21 and 23 isolating the thinfilm coils 20, 22 and an upper surface of the second magnetic layer 24is called an apex angle. This apex angle θ is one of important factorsfor determining the performance of the thin film magnetic head togetherwith the throat height TH and MR height MRH.

Furthermore, as shown in the plan view of FIG. 12, a width W of the poleportion 24 a of the second magnetic layer 24 is small. A width of tracksrecorded on a magnetic record medium is determined by said width W, andtherefore it is necessary to make this width W as small as possible inorder to realize a high surface recording density. It should be notedthat in the drawing, the thin film coils 20, 22 are denoted to beconcentric for the sake of simplicity.

As explained above, in order to improve the surface recording density onthe magnetic record medium, it is necessary to improve a performance ofthe thin film recording magnetic head comprising the first and secondmagnetic layers 17 and 24, gap layer 18 and thin film coil 20, 22. Inthe combination type thin film magnetic head having the reading magnetichead using the magnetoresistive element and the thin film recordingmagnetic head stacked one on the other, it is necessary to improve theperformance of the writing magnetic head as well as the reading magnetichead.

In order to improve the performance of the writing magnetic head, it isimportant that the throat height TH and apex angle θ shown in FIG. 10should be formed accurately such that they are not deviated from desireddesign values. However, in the known manufacturing method, it isdifficult to control these parameters precisely and to manufacture themagnetic head in accordance with desired design values. That is to say,the throat height TH is defined by a distance from the air bearingsurface 27 to an edge of the insulating layer 19 for isolating the thinfilm coil 20, 22, said edge opposing to the pole portion 24 a of thesecond magnetic layer 24. However, in an actual manufacturing process, aposition of said edge of the insulating layer 19 could not be clearlydefined, and the air bearing surface 27 is polished on the basis of athroat height zero position defined by the edge position under anassumption that said edge of the insulating layer 19 would be formed ata desired position. During the formation of the thin film coil 20, 22,the heating process is carried out at about 250° C., and the photoresistlayer constituting the insulating layer is melt and a pattern of theinsulating layer is varied. Therefore, a position of said edge of theinsulating layer is deviated from a desired position, and thus a valueof the throat height TH which corresponds to a length of the poleportion 24 a and is determined by using a position of the edge of theinsulating layer as a positional reference might be deviated from adesired design value. Particularly, when the photoresist layersconstituting the insulating layers 19, 21 and 23 are formed to have alarge thickness, said deviation in the pattern might amount to a verylarge value such as about 0.5 μm. Therefore, a fine throat height TH ofseveral microns to sub-microns could never be attained with a highreproducibility. Further, in case of using such a thick photoresistlayer, a desired pattern might be deviated by an unevenness in athickness. For instance, in a combination type thin film magnetic headfor a high frequency, a throat height TH has to be made not larger than1.0 μm. The above mentioned deviation of 0.5 μm is very large and anumber of defective throat heights TH are produced to decrease amanufacturing yield and a manufacturing cost is increased.

During the above mentioned heating process, the photoresist film of theinsulating layers 19, 21 and 23 is melt, and therefore a profile definedby side walls of these insulating layers as shown in FIG. 10 is variedand the apex angle θ is also varied. The apex angle θ influences theperformance of the thin film magnetic head and the deviation in the apexangle might sometimes cause a defect in the property of the thin filmmagnetic head. In this manner, in the known method of manufacturing thethin film magnetic head, it is difficult to improve the performance ofthe writing magnetic head. Such a problem would be manifest inaccordance with a progress in miniaturization of the thin film magnetichead.

The above explained demerit of the known method of manufacturing thethin film magnetic head is mainly due to the deviation in pattern of thephotoresist film caused by the process of heating the photoresist filmduring the formation of the thin film coil 20, 22, but this process isinevitable for flattening the surface of the insulating layer andisolating the coil windings.

Furthermore, although the performance of the reading magnetic head canbe improved by using a GMR reproducing element having a high sensitivityas the magnetoresistive element, in order to further increase a surfacerecording density, it is necessary to manufacture the magnetic head suchthat the MR height MRH defined by a height of the element measured fromthe air bearing surface 27 should not be deviated from a desired designvalue. In an actual manufacturing, the MR height MRH is determined by anamount of polishing the air bearing surface 27 like as the throat heightTH, and this polishing is carried out while a position of the edge ofthe insulating layer is used as a positional reference. Since a positionof the edge of the insulating layer is varied by the heating process asstated above, the MR height MRH is also varied and could not be formedto have a desired design value. Therefore, a manufacturing yield isdecreased by the variation in the MR height MRH, and a manufacturingcost is increased.

Particularly, in a combination type thin film magnetic head includingthe writing magnetic head and the reading magnetic head having themagnetoresistive element stacked one on the other, a balance between thethroat eight TH of the writing magnetic head and the MR height MRH ofthe reading magnetic head has to be taken into consideration. These twofactors are determined by a positional relationship of the insulatinglayers 19, 21 and 23 made of photoresist, a precision in the maskalignment of the MR reproducing element and a precision in the polishingprocess for forming the air bearing surface. Therefore, a patternalignment of the insulating layers 19 and 21 with respect to the MRlayer 15 should be carried out with a minimum error. However, althoughthis error could be minimum, there is still an error due to thedeformation in a pattern of the photoresist which constitutes theinsulating layers 19, 21 and 23 isolating the coil windings of the thinfilm coil 20, 22 by the heating process, and thus the throat height THand MR height MRH contain an error. Then, a balance between the writingmagnetic head and the reading magnetic head is broken and it is no morepossible to manufacture a combination type thin film magnetic headhaving a superior performance.

Moreover, as can be seen from FIG. 11, if a width of the first magneticlayer 17 and a width W of the pole portion 24 a of the second magneticlayer 24 near the air bearing surface 27 differ greatly from each other,there might be produced a leakage of a magnetic flux called a sidefringe magnetic flux. Particularly, in the combination type thin filmmagnetic head having the recording thin film magnetic head and the MRreproducing head 28 formed integrally, the first magnetic layer 17 alsoserves as the magnetic shield for the MR reproducing head, a width ofthe first magnetic layer has to be inherently larger than a width W ofthe pole portion 24 a of the second magnetic layer 24, and thereforethere might be induced a relatively large side fringe magnetic flux.When such a side fringe magnetic flux is produced, an undesired sidewrite phenomenon might occur and an effective width of a record track isincreased. In accordance with a recent progress in the high surfacerecording density, a track width has been shortened. but when the abovementioned side write occurs, there might be produced a cross talkbetween adjacent tracks as well as an accidental erase of amagnetization pattern recorded in adjacent tracks, so that asufficiently high surface recording density could not be realized.

In order to solve the above problems, there has been proposed toconstruct the trim structure by forming a protruded portion 17 a in thefirst magnetic layer 17 as shown in FIG. 13 and this protruded portionis formed to have a width identical with a width of the pole portion 24a of the second magnetic layer 24. Such a solution has been described inJapanese Patent Application Laid-open Publications, Kokai Hei 7-220245,7-225917 (corresponding to U.S. Pat. No. 5,438,747), 7-262519(corresponding to U.S. Pat. No. 5,438,747) and 7-296331.

Upon forming the protruded portion 17 a in the first magnetic layer 17shown in FIG. 13, in order to match a width of the protruded portion toa width of the pole portion 24 a of the second magnetic layer 24, afterforming the pole portion of the second magnetic layer, an ion beametching, for instance an ion milling is performed while the pole portionof the second magnetic layer is used as a mask to remove the gap layer18 and a portion of the first magnetic layer 17 is removed over a partof its thickness, for instance over about 500 nm. However, an etchingrate of the ion milling for an alumina constituting the gap layer 18 islow such as about 30 nm/minute, and therefore a long processing time isrequired and a through-put is liable to be decreased.

Furthermore, an etching rate of the ion milling for a permalloyconstituting the second magnetic layer 24 is high such as 200 nm/minute,and thus a thickness of the second magnetic layer 24 has to be larger byconsidering a reduction in thickness during the etching process. Thesecond magnetic layer 24 is formed by a plating, and therefore if athickness of the magnetic layer is larger, it is required to use a thickphotoresist film which is used for forming the pole portion 24 a inaccordance with a given pattern. When a thickness of the photoresistfilm is large, it is difficult to narrow a width W of the pole portion24 a, and a pole portion having a width of an order of sub-micron meterscould not be formed any more.

In order to form the protruded portion 17 a having the same dimension asthat of the pole portion 24 a of the second magnetic layer 24 by etchingthe gap layer 18 and first magnetic layer 17 with the ion milling, whilethe pole portion 24 a of the second magnetic layer 24 is used as a mask,an ion beam has to be made incident substantially at right angles.However, the ion milling is performed at right angles, debris of etchedmaterial might adhere to side walls of the protruded portion 17 a of thefirst magnetic layer 17 and pole portion 24 a of the second magneticlayer 24. By means of such adhered substances, the first and secondmagnetic layers 17 and 24 might be magnetically short-circuited and aneffective track width might be increased. Therefore, the thin filmmagnetic head having a desired performance could not be attained.

The inventors have proposed, in a co-pending U.S. patent applicationSer. No. 09/087,973 filed on Jun. 1, 1998, a solution for mitigating theabove mentioned problem of the undesired deposition of etched material.In this solution, the ion beam etching for digging a recess formed inthe write gap layer over a part of the thickness of the first magneticlayer 19 is carried out from an inclined direction. However, in thiscase, a side wall of the pole portion 24 a of the second magnetic layer24 might be also etched and a width of the pole portion might bedecreased. Then, a desired magnetic property could not be attained.

SUMMARY OF THE INVENTION

The present invention has for its object to provide a thin film magnetichead, in which a high surface recording density can be attained whiledesired characteristics are obtained, and the throat height THaccurately corresponding to desired design values can be obtainedstably.

It is another object of the invention to provide an improved combinationtype thin film magnetic head, in which a high surface recording densitycan be attained while desired characteristics are obtained, and thethroat height TH and MR height MRH accurately corresponding to desireddesign values can be obtained stably.

It is another object of the invention to provide a method ofmanufacturing the above mentioned thin film magnetic head andcombination type thin film magnetic head having the above mentionedsuperior characteristics in an accurate manner with a high yield.

According to the invention, a thin film magnetic head comprises:

a first magnetic layer having a pole portion which is opposed to amagnetic record medium and defines a width of record tracks on themagnetic record medium;

a second magnetic layer having a pole portion whose end surfaceconstitutes an air bearing surface together with said pole portion ofthe first magnetic layer, said second magnetic layer being magneticallycoupled with said first magnetic layer at a rear portion remote fromsaid air bearing surface;

side walls made of a non-magnetic material and being provided at leaston side surfaces of said pole portion of the second magnetic layer;

a gap layer made of a non-magnetic material and being interposed betweensaid pole portion of the first magnetic layer and said pole portion ofthe second magnetic layer;

a thin film coil having a portion which is supported by an insulatingmaterial in an electrically isolated manner between said first magneticlayer and said second magnetic layer; and

a substrate supporting said first and second magnetic layers, gap layer,insulating layer and thin film coil;

wherein a recess having an inner side wall which defines a positionalreference for the air bearing surface is provided in a vicinity of theside surfaces of the first and second magnetic layers such that saidrecess penetrates through said gap layer and extends into said firstmagnetic layer over a part of a thickness of said first magnetic layer.

According to the invention, a method of manufacturing a thin filmmagnetic head comprises the steps of:

forming a first magnetic layer having a pole portion such that the firstmagnetic layer is supported by a substrate;

forming a thin film coil above said first magnetic layer such that thethin film coil is supported by an insulating layer in an electricallyisolated manner;

forming a gap layer made of a non-magnetic material at least on saidpole portion of the first magnetic layer and said insulating layer;

forming a second magnetic layer on said gag layer, said second magneticlayer having a pole portion which is opposed to said pole portion of thefirst magnetic layer via said gap layer;

forming side walls made of a non-magnetic material at least on sidesurfaces of said pole portion of said second magnetic layer;

performing an anisotropic etching to remove a portion of said gap layeradjacent to side edges of said pole portion of the second magnetic layerby using said pole portion of the second magnetic layer, said side wallsand a photoresist layer provided on said gap layer as a mask to form arecess in said gap portion;

performing an etching to remove a portion of said first magnetic layerby using said pole portion of the second magnetic layer and said sidewalls as a mask such that said recess is dug down partially into thefirst magnetic layer; and

polishing the substrate, pole portions of the first and second magneticlayers and gap layer sandwiched by these magnetic layers to form an airbearing surface which is to be opposed to a magnetic record medium,while an inner side wall of said recess is used as a positionalreference.

Further, according to the invention, a method of manufacturing a thinfilm magnetic head comprises the steps of:

forming a first magnetic layer having a pole portion such that the firstmagnetic layer is supported by a substrate;

forming a gap layer made of a non-magnetic material on said firstmagnetic layer;

forming a thin film coil such that the thin film coil is supported by aninsulating layer in an electrically isolated manner;

forming a second magnetic layer having a pole portion which is opposedto said pole portion of the first magnetic layer via said gap layer;

forming side walls made of a non-magnetic material at least on sidesurfaces of said pole portion of said second magnetic layer;

performing an anisotropic etching to remove a portion of said gap layeradjacent to side edges of said pole portion of the second magnetic layerby using said pole portion of the second magnetic layer, said side wallsand a photoresist layer provided on said gap layer as a mask to form arecess in said gap portion;

performing an etching to remove a portion of said first magnetic layerby using said pole portion of the second magnetic layer and said sidewalls as a mask such that said recess is dug down partially into thefirst magnetic layer; and

polishing the substrate, pole portions of the first and second magneticlayers and gap layer sandwiched by these magnetic layers to form an airbearing surface which is to be opposed to a magnetic record medium,while an inner side wall of said recess is used as a positionalreference.

In the thin film magnetic head according to the invention, it is no morenecessary to polish the air bearing surface by using a position of anedge of the insulating layer which supports the thin film coil in anelectrically isolated manner as a positional reference, and thepolishing process can be performed by using the inner side wall of therecess as a positional reference. A position of the inner side wall ofthe recess can be defined very accurately on the basis of a position ofthe edge of the insulating layer in regardless of a variation of aposition of this edge, and moreover the inner side wall of the recesscan be inspected under a microscope which is installed in a polishingmachine during the polishing. Therefore, a position of the air bearingsurface can be precisely determined, and a throat height TH which isidentical with a length of the pole portion of the second magnetic layercan be formed accurately to follow a desired design value. Moreover,since the side walls made of a non-magnetic material are formed on theside surfaces of the pole portion of the second magnetic layer, adimension of this pole portion does not deviate during the manufacturingprocess. In this manner, it is possible to attain the thin film magnetichead having an excellent performance.

It should be noted that according to the invention, the pole portion ofthe first magnetic layer is formed into the trim structure, andtherefore a leakage of a magnetic flux during writing, i.e. the sidefringe magnetic flux can be reduced and a track width can be narrowed.Then, the thin film magnetic head according to the invention can realizea very high surface recording density.

In the method of manufacturing the thin film magnetic head according tothe invention, after selectively removing by an anisotropic etching aportion of the gap layer while the pole portion of the second magneticlayer, side walls and photoresist layer formed on the gap layer are usedas a mask to form the recess in the gap layer, a portion of the firstmagnetic layer exposed in the recess is etched by, for instance an ionmilling such that the recess is dug down into the first magnetic layerover a part of a whole thickness of the first magnetic layer. An etchingrate of the anisotropic etching for the gap layer is high such as 200nm/minute, and therefore the etching process can be completed within ashort time period and a high through put can be attained. Furthermore,during this anisotropic etching, a thickness of the pole portion of thesecond magnetic layer is not substantially reduced, and thus it is nomore necessary to form this pole portion to have an unnecessarily largethickness. As a result thereof, a miniaturization can be attained and awidth of the pole portion can be small.

In a preferable embodiment of the thin film magnetic head according tothe invention, said insulating layer isolating a portion of the thinfilm coil situating between said first and second magnetic layers iscovered with said gap layer made of a non-magnetic material. Bysurrounding the insulating layer of the thin film coil with the gaplayer, a position of the edge of the insulating layer is hardly shifted,and therefore said inner side wall of the recess can be formedaccurately with reference to a position of the edge of the insulatinglayer.

In another preferable embodiment of the thin film magnetic headaccording to the invention, the magnetic head is constructed as acombination type thin film magnetic head by providing a readingmagnetoresistive element between said substrate and said first magneticlayer such that the magnetoresistive element is electrically isolatedand magnetically shielded and an edge of the element is exposed on theair bearing surface.

In such a combination type thin film magnetic head having the thin filmwriting magnetic head and thin film reading magnetic film stacked one onthe other, the above mentioned balance between the throat height TH andthe MR height MRH can be always maintained to be a desired one, and thecombination type thin film magnetic head having a high performance canbe realized.

In the method according to the invention, after selectively removing byan anisotropic etching a portion of the gap layer while the pole portionof the second magnetic layer, side walls and a photoresist layer formedon the gap layer are used as a mask to form the recess in the gap layer,a portion of the first magnetic layer exposed in the recess is etchedsuch that the recess is dug down over into the first magnetic layer overa part of a whole thickness of the first magnetic layer, and saidetching is performed by an ion beam etching such as ion milling. Byconducting the ion beam etching at an angle of 40-70°, particularlyabout 45° with respect to a normal to the first magnetic layer, debrisof etched magnetic material is prevented from being applied again ontothe side walls of the pole portion such that the first and secondmagnetic layers are scarcely short-circuited and an effective trackwidth could not be increased. Moreover, according to the invention, theside surfaces of the pole portion of the second magnetic layer arecovered with the side walls made of a non-magnetic material, even if theion milling is performed from an inclined direction, the pole portion isno more thinned. Then, debris of etched substances are not adhered tothe to the pole portion and the magnetic characteristics of the thinfilm magnetic head according to the invention can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-10 are cross sectional views showing successive steps ofmanufacturing a known combination type thin film magnetic head;

FIGS. 11 and 12 are front and plan views, respectively illustrating theknown thin film magnetic head;

FIG. 13 is a cross sectional view illustrating a known thin filmmagnetic head having the pole portion with the trim structure;

FIGS. 14A and 14B-21A and 21B are cross sectional views showingsuccessive steps of an embodiment of the thin film magnetic headmanufacturing method according to the invention;

FIG. 22 is a plan view of the magnetic head;

FIG. 23 is a perspective view depicting the recess formed in thevicinity of the pole portion;

FIG. 24 is a perspective view showing a condition in which the recess isdug down into the underlying first magnetic layer over a part of a wholethickness thereof;

FIG. 25 is a cross sectional view depicting the condition of FIG. 24;

FIG. 26 is a perspective view illustrating the pole portion of the thinfilm magnetic head having the air bearing surface;

FIG. 27 is a cross sectional view showing the magnetic head shown inFIG. 26;

FIG. 28 is a cross sectional views illustrating another embodiment ofthe thin film magnetic head according to the invention; and

FIG. 29 is a perspective view showing a condition in which the airbearing surface is formed.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 14-27 show successive steps of an embodiment of the method ofmanufacturing the thin film magnetic head according to the invention. InFIGS. 14-21, A represents a cross sectional view cut along a lineperpendicular to the air bearing surface and B illustrates a crosssectional view cut along a line parallel with the air bearing surface.It should be noted that in these drawings, dimensions of variousportions are not shown in accordance with actual relationship.Furthermore, in an actual process for manufacturing the thin filmmagnetic head, since a number of thin film magnetic heads are formed ina wafer, an end face of the magnetic head is not exposed, but for thesake of explanation, an end face is shown in the drawings.

At first, as shown in FIG. 14, on a substrate 41 made of an AlTiC andhaving a thickness of several millimeters, is deposited an insulatinglayer 42 made of an alumina having a thickness of about 3-5 μm. Next, asillustrated in FIG. 15, a permalloy layer 43 constituting a lowermagnetic shield for an MR element is deposited to have a thickness of2-3 μm by using a photoresist film as a mask by means of a plating.

After forming an alumina layer 44 having a thickness of 4-6 μm onexposed surfaces of the permalloy layer 43 and alumina insulating layer42, a surface is flattened by a mechanical polishing or chemicalmechanical polishing (CMP) as depicted in FIG. 16.

Next, a MR film 46 having the magnetoresistive effect is formed inaccordance with a desired pattern such that the MR film is embeddedwithin a shield gap film 45. Then, a first magnetic layer 47 made of apermalloy and having a thickness of 2-4 μm is selectively formed on theshield gap layer, said first magnetic layer constituting a bottom poleof the thin film writing magnetic head. Further, in order to remove astep or steps formed in a surface, after forming an alumina layer havinga thickness of 5-6 μm on the first magnetic layer, thechemical-mechanical polishing CMP is conducted to expose an flattenedsurface of the first magnetic layer 47 as illustrated in FIG. 17. Itshould be noted that a pair of electrical conductors for constructing anelectrical connection to the MR film 46 embedded in the shield gap layer45 are formed, but the conductors are not shown in the drawing.

Next, a gap layer 48 made of alumina is formed to have a thickness of150-300 nm, and then an insulating layer 49 made of a photoresist anddefining an apex angle θ is formed in accordance with a given pattern asshown in FIG. 18. Then, as illustrated in FIG. 19, a thin film coil 50,52 made of a copper is formed on the insulating layer 49 such that thethin film coil is supported by insulating layers 51 and 53 in anelectrically isolated manner. Here, an recess 47 a is formed in theinsulating layers 49, 51, 53 for constituting a closed magnetic path bymagnetically coupling the first magnetic layer 47 and a second magneticlayer to be formed in a later process. The thin film coil may be formedby an electroplating, and the electroplating method is identical with aknown method and its explanation is dispensed with.

Next, as depicted in FIG. 20, a second magnetic layer 54 having athickness of 3-4 μm is deposited, and then the second magnetic layer 54is selectively removed by using a photoresist layer having a desiredpattern to form a pole portion 54 a. The pole portion 54 a is preferablyformed to have a width not larger than 2 μm, particularly not largerthan 1 μm.

During the formation of the second magnetic layer 54, a magneticmaterial is also deposited in the opening 47 a, and the first and secondmagnetic layers 47 and 54 are magnetically coupled with each other viathe opening.

Next, a non-magnetic layer 55 is formed on the top surface and sidesurfaces of the second magnetic layer 54 as well as on the exposedsurface of the gap layer 48. Said non-magnetic layer 55 has a thicknessof, for instance 150-300 nm. Then, after the nonmagnetic layer 55 iscovered with a photoresist except for a portion applied on the poleportion 54 a, an anisotropic etching to form side walls 55 a on the sidesurfaces of the pole portion 54 a.

Next, as shown in FIGS. 21-23, the gap layer 48 is partially removed toform a recess or opening 56 by an anisotropic etching, in the presentembodiment a reactive ion etching (RIE) using a high density plasmasource, while the pole portion 54 a of the second magnetic layer 54, theside walls 55 a formed on the side surfaces of the pole portion 54 a anda photoresist layer having a recess or opening formed in the vicinity ofthe pole portion 54 a of the second magnetic layer 54 are used as amask. The reactive ion etching may be conducted within an atmosphere of,for instance CF₄, BCl₃, Cl₂ or BCL₃+Cl₂. It is particularly preferableto perform the reactive ion etching within an atmosphere of BCL₃ or amixture of BCl₃ and Cl₂. In case of using a mixture of BCl₃ and Cl₂, anamount of Cl₂ is preferably not higher than 50%.

An etching rate of the gap layer 48 made of an alumina for the reactiveion etching is high such as 100-300 nm/minute, and therefore an etchingtime of 1-2 minutes for forming the recess 56 in the gap layer 48 issufficient. Furthermore, upon forming the recess 56, a line A—A passingthrough edges of the insulating layers 49, 51, 53 opposing to the poleportion, that is to say a position of the zero throat height is used asa positional reference such that a side wall of the recess 56 remotefrom the air bearing surface, i.e. an inner side wall 56 a of the recess56 becomes coincided with a line B—B which is separated from the lineA—A by a given distance. Since when the gap layer 48 is etched to formthe recess 56, the overcoat layer (see FIG. 9) is not formed yet, theedges of the insulating layers 49, 51, 53 opposing to the pole portioncan be seen by means of, for instance a microscope. Therefore, theposition B—B of the inner side wall 56 a of the recess 56 can beaccurately formed by using the edges of the insulating layers as apositional reference.

After forming the recess 56 by selectively removing the gap layer 48 bythe anisotropic etching as stated above, an ion beam etching is carriedout while the photoresist layer and side walls 55 a which have been usedas a mask for the reactive ion etching is remained. In this manner, therecess 56 is dug down partially into the first magnetic layer 47 to formthe trim structure at the pole portion of the first magnetic layer asillustrated in FIGS. 24 and 25. In the present embodiment, an ionmilling is used as this ion beam etching, and the recess 56 is dug downinto the first magnetic layer 47 over about 500-800 nm. By forming thetrim structure, it is possible to prevent a side fringe magnetic fluxleaked out of side walls of the pole portion 54 a of the second magneticlayer 54, and the performance can be further improved.

The above mentioned anisotropic etching and ion milling are conductedwhile the pole portion 54 a of the second magnetic layer 54 is used as amask, but according to the invention, since the side walls 55 a areformed on the side surfaces of the pole portion 54 a, the pole portionis not thinned. Further, the photoresist layer used in the RIE processmay be removed prior to the etching process of ion-trimming the firstmagnetic layer 47. In this case, after digging down the recess partiallyinto the first magnetic layer 47, the gap layer 48 is removed except fora portion under the second magnetic layer 54.

It has been known to form the trim structure in the surface of the firstmagnetic layer 47 by etching the first magnetic layer by the ion beametching such as the ion milling. However, in the prior art technique,the ion beam is made incident upon the magnetic layer perpendicularly.When the ion beam is made incident upon the magnetic layer at rightangles, magnetic materials are liable to be adhered to side walls andupper surface of the pole portion, and the first and second magneticlayer might be short-circuited and an effective track width might beincreased. According to the invention, in order to remove such aproblem, the ion beam is made incident upon the first magnetic layer atan incident angle of preferably of 40-70°, particularly about 45° withrespect to a normal to the surface of the first magnetic layer. Byperforming the ion beam etching from such an inclined direction, theabove mentioned adherence of etched magnetic material can be effectivelyprevented. Moreover, according to the invention, the side surfaces ofthe pole portion 54 a are covered with the side walls 55 a made of anon-magnetic material, and therefore the pole portion can be effectivelyprotected against the etching from the inclined direction.

As explained above, in the present embodiment, upon forming the recess56, since the gap layer 48 has been removed by the reactive ion etchingand the side surfaces of the pole portion 54 a of the second magneticlayer 54 are covered with the non-magnetic side walls 55 a, the etchingprocess for partially removing the first magnetic layer 47 can becarried out from an inclined direction. Therefore, it is possible torealize a thin film magnetic head having a smaller effective trackwidth, in which the adhesion of magnetic materials and the magneticshort-circuit between the first and second magnetic layers 47 and 54 canbe avoided. Further, undesired variation in a width of the pole portion54 a can be prevented by the side walls 55 a.

Next, the substrate 41, alumina insulating layer 42, bottom shield layer43, shield gap layer 45, magnetoresistive film 46, first magnetic layer47, gap layer 48 and second magnetic layer 54 are polished up to aposition indicated by a line C—C in FIG. 22 to form an air bearingsurface 57 as depicted in a perspective view of FIG. 26 and a crosssectional view of FIG. 27. During this polishing process, the inner sidewall 56 a of the recess 56 can be monitored with a microscope arrangedon a polishing machine, and thus the polishing can be performedautomatically and accurately while the inner side wall is used as apositional reference. In this manner, the pole portion 54 a having anaccurate dimension can be obtained. That is to say, the inner side wall56 a of the recess 56 is separated from the edges of the insulatinglayers 49, 51, 53 by a predetermined distance and the air bearingsurface 57 is formed while the inner side wall of the recess is as thepositional reference. Therefore, a distance from the edges of theinsulating layers to the air bearing surface 57 (a distance between theline A—A and the line B), that is to say a throat height TH can beformed accurately to have a desired design value. This throat height THis preferable not longer than 2 μm, particularly not longer than 1 μm.According to the invention, the inner side wall 56 a of the recess 56has to be situated at a position which is inner than the air bearingsurface 57, and the inner side wall 56 a is still existent after thepolishing process.

Further, according to the invention, the magnetoresistive film 46 isalso polished during the polishing process for forming the air bearingsurface 56 to form the MR reproducing element 58. As stated above,according to the invention, this polishing process is carried out byusing a position of the inner side wall 56 a of the recess 56 formed inthe gap layer 48 as a reference position (line A—A) and this inner sidewall is formed by using a position of the edge of the insulating layer49, 51, 53 as a reference position, and therefore the MR height MRH canbe also formed accurately to have a desired design value. Moreover,according to the invention, since a desired relationship cab alwaysattained between the MR height MRH and the throat height TH, theseparameters can be kept in an optimally balanced condition and acombination type thin film magnetic head can be obtained.

FIGS. 28 and 29 are cross sectional and perspective views showinganother embodiment of the thin film magnetic head according to theinvention. In the present embodiment, portions similar to those of theprevious embodiment are denoted by the same reference numerals used inthe previous embodiment. In the previous embodiment, after forming thegap layer 48 on the first magnetic layer 47, the insulating layer 49 isformed on the gap layer 48 and then the thin film coil 50, 52 is formedon the insulating layer 49 such that the thin film is isolated by theinsulating layers 51, 53. In the present embodiment, after theinsulating layer 49 has been formed on the first magnetic layer 47 andthen the thin film coil 50, 52 isolated by the insulating layers 51, 53has been formed on the insulating layer 49, the gap layer 48 is formedon the exposed surface of the first magnetic layer 47 as well as on theinsulating layers 51, 53. After that, the second magnetic layer 54 isformed on the gap layer 48 in accordance with a desired pattern.

Next, the non-magnetic layer 55 is applied on the exposed surface of thegap layer 48 as well as on the top surface and side surfaces of thesecond magnetic layer 54. Then, the non-magnetic layer 55 is subjectedto the anisotropic etching while the photoresist layer is used as a maskto form the side walls 55 a on the side surfaces of the pole portion 54a of the second magnetic layer 54 as shown in FIG. 28.

After that, the recess 56 is formed in the gap layer 48 by theanisotropic etching, and then the recess 56 is dug down into the firstmagnetic layer 47 over a part of its thickness. Then, the polishingprocess is carried out while the inner side wall 56 a of the recess 56is used as the positional reference to form the air bearing surface 57as shown in FIG. 29. It should be noted that in FIG. 29, non-magneticlayer 55 except for the side walls 55 a is dispensed with for the sakeof simplicity.

In the present embodiment, since the insulating layers 49, 51, 53covering the thin film coil 50, 52 are covered with the gap layer 53which is hardly affected by the heating process, a profile of theinsulating layers is not varied. Therefore, it is possible to obtain anapex angle θ which follows a desired design value. In this manner, theperformance of the thin film writing magnetic head can be improved.Moreover, since the gap layer 48 is formed such that the insulatinglayers 51, 53 are covered with the gap layer, during a heating processfor removing the photoresist layer by ashing after patterning the secondmagnetic layer 54, the insulating layers 51, 53 are protected by the gaplayer 48, and the thin film coil 50, 52 is neither exposed norshort-circuited without increasing a thickness of the insulating layers.

The present invention is not limited to the above mentioned embodiments,but many alternations and modifications may be considered within thescope of the invention. For instance, in the above embodiments, thesubstrate is made of AlTiC which is a mixture of alumina-titan carbide,but the substrate may be made of other material such as alumina, Si,SiO₂, BN, ceramics and diamond-like carbon. Further, themagnetoresistive element may be GMR element instead of AMR element.Moreover, the gap layer 53 may be made of other non-magnetic materialthan alumina such as SiO₂, SiN and oxynitride. Furthermore, in the aboveexplained embodiments, the magnetic layers 47, 54 is made of a permalloywhich is an alloy based on Fe—Ni, but may be made of other magneticmaterial such as Co—Zr—Sn based alloy, Fe—Zr—N based alloy, Fe—Ta—Cbased alloy, Co—Zr—Nb and FeN.

In the above embodiments, the thin film magnetic head is constructed asa combination type thin film magnetic head having the inductive typethin film writing magnetic head and MR reproducing element stacked oneon the other, but it may be constructed as the inductive type thin filmwriting magnetic head.

Also in the above embodiments, the recess formed in the gap layer is dugdown partially into the first magnetic layer by the ion milling, butaccording to the invention, any other ion beam etching may be utilized.Furthermore, this etching may be a reactive ion etching. In this case,after forming the opening in the gap layer by a reactive ion etching,the opening may be dug down partially into the first magnetic layerwithout interrupting the reactive ion etching, and thus a processbecomes further simple.

In the thin film magnetic head and the method of manufacturing the sameaccording to the invention, since the recess having the inner side wallwhich serves as a positional reference for the air bearing surface isformed in the gap layer at a portion adjacent to the pole portion of thesecond magnetic layer, it is possible to form the throat height TH tohave a desired design value by polishing the air bearing surface on thebasis of the inner side wall of the recess. In case of the combinationtype thin film magnetic head including the thin film reading magnetichead having the MR reproducing element, not only the MR height MRH canbe accurately formed to have a desired design value, but also a goodbalance between the MR height MRH and the throat height TH can be alwaysattained and the performance of the combination type thin film magnetichead can be easily improved.

The trim structure can be obtained by digging down the opening into thefirst magnetic layer over a part of a whole thickness thereof, andtherefore an undesired leakage of a magnetic flux can be prevented. Uponforming the recess, the gap layer is removed by an anisotropic etchinghaving a high etching rate for the gap layer material, an etching timecan be shortened and a reduction in a thickness of the second magneticlayer during the etching can be decreased. Therefore, a width of thepole portion can be reduced and a very narrow track width of sub-micronorder can be realized. Further, after removing the gap layer by ananisotropic etching, the first magnetic layer can be removed by an ionbeam etching from an inclined direction, and thus the first and secondmagnetic layers can be effectively prevented from being magneticallyshort-circuited by an adhesion of magnetic materials and the performanceof the thin film magnetic head can be improved. According to theinvention, since the side surfaces of the pole portion of the secondmagnetic layer are covered with the side walls made of a non-magneticmaterial, the pole portion can be effectively prevented from beingthinned during the ion beam etching from an inclined direction. In thismanner, it is possible to form the pole portion having a preciselydefined dimension, and thus it is possible to provide the improved thinfilm magnetic head having desired characteristics.

Moreover, in the second embodiment, since the insulating layer isolatingthe thin film coil is covered with the gap layer, a pattern of theinsulating layer is hardly deformed due to a melting of an edge of theinsulating layer, and a position of the edge of the insulating layerserving as a positional reference for a throat height can be definedaccurately. Since a position of the inner side wall of the recess isformed on the basis of said positional reference and the air bearingsurface is polished on the basis of a position of the inner side wall ofthe recess, a throat height TH can be formed accurately. Furthermore,since a profile of the insulating layer covering the thin film coil ishardly deviated, an apex angle θ can be also formed to have a desireddesign value. Moreover, the MR element is formed also on the basis ofthe inner side wall of the recess, a desired positional relationshipbetween the throat height TH and the MR height MRH can be alwaysmaintained, and a balance between these factors can be optimized.

As explained above, according to the invention, it is possible toprovide a thin film magnetic head having a high performance, in whichthroat height TH, apex angle θ and MR height MRH are formed to havedesired values. Particularly, according to the invention, it is possibleto provide a miniaturized thin film magnetic head which can realize anarrow track width within a range from several micron meters tosub-micron meters. Upon manufacturing, it is possible to obtain a thinfilm magnetic head having desired design values, and thus amanufacturing yield is improved and a manufacturing cost can be reduced.

What is claimed is:
 1. A method of manufacturing a thin film magnetichead, comprising the steps of: forming a first magnetic layer having apole portion such that the first magnetic layer is supported by asubstrate; forming a thin film coil above said first magnetic layer suchthat the thin film coil is supported by an insulating layer in anelectrically isolated manner; forming a gap layer made of a non-magneticmaterial at least on said pole portion of the first magnetic layer andsaid insulating layer; forming a second magnetic layer on said gaplayer, said second magnetic layer having a pole portion which is opposedto said pole portion of the first magnetic layer via said gap layer;forming side walls made of a non-magnetic material at least on sidesurfaces of said pole portion of said second magnetic layer; performinga reactive ion etching to remove a portion of said gap layer adjacent toside edges of said pole portion of the second magnetic layer by usingsaid pole portion of the second magnetic layer, said side walls and aphotoresist layer provided on said gap layer as a mask to form a recessin said gap layer; performing an ion beam etching to remove a portion ofsaid first magnetic layer by using said pole portion of the secondmagnetic layer and said side walls as a mask such that said recess isdug down partially into the first magnetic layer; and polishing thesubstrate, pole portions of the first and second magnetic layers and gaplayer sandwiched by these magnetic layers to form an air bearing surfacewhich is to be opposed to a magnetic record medium, while an inner sidewall of said recess is used as a positional reference.
 2. The methodaccording to claim 1, wherein said reactive ion etching is conductedwithin an atmosphere of an etching gas selected from the groupconsisting of CF₄, BCl₃, Cl₂ and BCl₃+Cl₂.
 3. The method according toclaim 1, wherein said reactive ion etching is conducted within anatmosphere including BCL₃ and Cl₂, a content of Cl₂ not exceeding 50%.4. The method according to claim 1, wherein said ion beam etching isconducted from a direction which is inclined with respect to a linewhich is normal or perpendicular to the first magnetic layer by 40-70°.5. The method according to claim 4, wherein said ion beam etching isconducted from a direction which is inclined with respect to a linewhich is normal or perpendicular to the first magnetic layer by about45°.
 6. The method according to claim 1, wherein the etching for diggingthe recess into the first magnetic layer is performed by a reactive ionetching.
 7. The method according to claim 1, wherein said step offorming the side walls on the side surfaces of the pole portion of thesecond magnetic layer includes a step of forming a non-magnetic layer ontop surfaces and side surfaces of the second magnetic layer, a step ofcovering a part of said non-magnetic layer except for portions depositedon the side surfaces of the pole portion of the second magnetic layerwith a photoresist and a step of performing anisotropic etching toselectively remove the non-magnetic layer except for the portionsdeposited on the side surfaces of the pole potion of the second magneticlayer.
 8. The method according to claim 1, wherein a combination typethin film magnetic head is constructed by forming a readingmagnetoresistive element between said substrate and said first magneticlayer in an electrically isolated and magnetically shielded manner. 9.The method according to claim 8, wherein a third magnetic layer formagnetic shielding is formed on said substrate, and after forming amagnetoresistive material film is formed on said third magnetic layersuch that the magnetoresistive material film is embedded in a secondinsulating layer, said first magnetic layer is formed on said secondinsulating layer, and during the step of polishing said air bearingsurface, said magnetoresistive material film is polished together withsaid third magnetic layer to form said magnetoresistive element whoseside edge is exposed on the air bearing surface.
 10. A method ofmanufacturing a thin film magnetic head, comprising the steps of:forming a first magnetic layer having a pole portion such that the firstmagnetic layer is supported by a substrate; forming a gap layer made ofa non-magnetic material on said first magnetic layer; forming a thinfilm coil such that the thin film coil is supported by an insulatinglayer in an electrically isolated manner; forming a second magneticlayer having a pole portion which is opposed to said pole portion of thefirst magnetic layer via said gap layer; forming side walls made of anon-magnetic material on side surfaces of said pole portion of saidsecond magnetic layer; performing a reactive ion etching to remove aportion of said gap layer adjacent to side edges of said pole portion ofthe second magnetic layer by using said pole portion of the secondmagnetic layer, said side walls and a photoresist layer provided on saidgap layer as a mask to form a recess in said gap layer; performing anion beam etching to remove a portion of said first magnetic layer byusing said pole portion of the second magnetic layer and said side wallsas a mask such that said recess is dug down partially into the firstmagnetic layer; and polishing the substrate, pole portions of the firstand second magnetic layers and gap layer sandwiched by these magneticlayers to form an air bearing surface which is to be opposed to amagnetic record medium, while an inner side wall of said recess is usedas a positional reference.